I am replacing a leaking 40 gallon reliance gas water heater. The former owner put in a regular (not power or direct vent water heater) illegally. I want to replace the heater with a power vent model but there is no electricity in tbe closet. In addition, if there is a power outage, there will be not hot water. There is the proper thimble vent pipe situated in the closet to connect the exhaust pipe to. I want to know if I can put a direct vented water heater in the place of a power vented heater. Thank you.

no electricity in tbe closet

You will have to install a outlet

in the event that there is a power outage, there will be not hot water

Correct. You will be showering with cold water.

A direct vent heater is just what it says. You CANNOT hook to a thimble in the closet. You will have to make a hole in the wall to the outside and DIRECT VENT IT. That is why they call them direct vent.

I do not have one. I do not want one. The regular water heaters work well without the problems associated with direct vent.

Buy a large UPS for your computer and use it to power your tank during a power outage. It should give your tank a few recovery cycles before draining the battery.

Wish I did not have my direct vent B&W, but that's what you get with Contemporary architectures.